The purpose of the proposed project is to longitudinally and comprehensively investigate the nature of communicative impairment in patients with Alzheimer's dementia (DAT) who have been carefully evaluated as to (a) age of disease onset, (b) presence of extrapyramidal symptomatology, (c) family history of DAT, (d) rate of disease progression, and (e) dementia severity. Reports of variation in the clinical behavior of DAT patients in relation to the aforementioned variables have heen sufficiently compelling to motivate the NINCDS-ADRDA sponsored work group to recommend their use by researchers in the description of DAT patients. To date, these criteria have not been used for differentiating DAT patients in a study of communicative functioning. The proposed study has been designed to determine the existence of linguistically unique subgroups within the DAT population should they exist. An extensive communication test battery will be administered once yearly for five years to DAT patients and normal subjects. Ninety DAT subjects with early disease onset and 90 with late onset will be identified and subdivided according to level of severity as determined by the Global Deterioration Scale. Two normal control groups matched in age to the early and late DAT onset subject groups will be formed. Medical and neurological evaluations will be conducted prior to the communication evaluation and a family member will be interviewed about medical and familial history. Information from medical examinations and family interviews will be used to classify subjects according to the aforementioned variables. The distributional characteristics of the data will be calculated and a principal components factor analysis employed for data reduction. Determination of relations between the classification variables and communication test performance will be made through multivariate analysis of variance and multiple regression. The study will produce the first well-documented natural history of linguistic dissolution of DAT patients controlled for severity, age, family history, extrapyramidal symptomatology, and rate of disease progression. Clinicians will have extensive information about the diagnostic efficacy of a wide range of communication measures and their suitability for use with different types of DAT patients. Finally, baseline data about communicative functioning of DAT patients will be available to clinicians desirous of testing the efficacy of various therapies.